Add paranoid:swim to prevent typoing into water or lava

In the name of accessibility: Prevent moving into dangerous liquids.

Now with themed rooms, water and lava are more common, and it's
unreasonable to expect blind players to check every step for those.
With paranoid:swim, just prevent normal walking into those liquids,
unless you prefix the movement with 'm', or if the liquid would not
harm you.

Doesn't completely prevent an accidental dunking - for example
if the hero is impaired or couldn't see the liquid.

This comes from xNetHack by copperwater <aosdict@gmail.com>
with some changes to the code.

doc/Guidebook.mn

@@ -4054,6 +4054,8 @@ than immediately praying; on by default;
 .PL Remove
 require selection from inventory for \(oqR\(cq and \(oqT\(cq
 commands even when wearing just one applicable item.
+.PL swim
+prevent walking into water or lava.
 .PL all
 turn on all of the above.
 .PE
@@ -5508,6 +5510,8 @@ If this is the case, disable the
 .op number_pad
 option and use the traditional
 Rogue-like commands.
+.lp paranoid_confirmation:swim
+Prevent walking into water or lava.
 .lp autodescribe
 Automatically describe the terrain under the cursor when targeting.
 .lp mention_walls

doc/Guidebook.tex

@@ -4430,6 +4430,8 @@ \subsection*{Customization options}
 \item[{\tt Remove~}] require selection from inventory for `{\tt R}'
 and `{\tt T}'
 commands even when wearing just one applicable item.
+\item[{\tt swim~~~}]
+prevent walking into water or lava.
 \item[{\tt all~~~~}]
 turn on all of the above.
 \elist
@@ -6054,6 +6056,9 @@ \subsection*{Configuring {\it NetHack\/} for Play by the Blind}
 If this is the case, disable the number\verb+_+pad option and use the
 traditional Rogue-like commands.
 %.lp
+\item[\ib{paranoid\verb+_+confirmation:swim}]
+Prevent walking into water or lava.
+%.lp
 \item[\ib{autodescribe}]
 Automatically describe the terrain under the cursor when targeting.
 %.lp

doc/fixes3-7-0.txt

@@ -1410,6 +1410,7 @@ reading a blessed scroll of light has a chance to improve bless/curse state
 	of wielded Sunsword or worn gold dragon scales/mail similar to dipping
 	those into holy water; cursed scroll has chance to worsen the state
 added a chronicle of major events, and optional live logging of those
+paranoid:swim to prevent accidental dunking into dangerous liquids
 
 
 Platform- and/or Interface-Specific New Features

include/context.h

@@ -150,6 +150,7 @@ struct context_info {
     boolean botlx;       /* print an entirely new bottom line */
     boolean door_opened; /* set to true if door was opened during test_move */
     boolean enhance_tip; /* player is informed about #enhance */
+    boolean swim_tip;    /* player was informed about walking into water */
     struct dig_info digging;
     struct victual_info victual;
     struct engrave_info engraving;

include/flag.h

@@ -78,6 +78,7 @@ struct flag {
 #define PARANOID_BREAKWAND  0x0080
 #define PARANOID_WERECHANGE 0x0100
 #define PARANOID_EATING     0x0200
+#define PARANOID_SWIM       0x0400
     int pickup_burden; /* maximum burden before prompt */
     int pile_limit;    /* controls feedback when walking over objects */
     char discosort;    /* order of dodiscovery/doclassdisco output: o,s,c,a */
@@ -466,6 +467,8 @@ enum runmode_types {
 /* continue eating: prompt given _after_first_bite_ when eating something
    while satiated */
 #define ParanoidEating ((flags.paranoia_bits & PARANOID_EATING) != 0)
+/* Prevent going into lava or water without explicitly forcing it */
+#define ParanoidSwim ((flags.paranoia_bits & PARANOID_SWIM) != 0)
 
 /* command parsing, mainly dealing with number_pad handling;
    not saved and restored */

include/mondata.h

@@ -38,6 +38,7 @@
 #define is_floater(ptr) ((ptr)->mlet == S_EYE || (ptr)->mlet == S_LIGHT)
 /* clinger: piercers, mimics, wumpus -- generally don't fall down holes */
 #define is_clinger(ptr) (((ptr)->mflags1 & M1_CLING) != 0L)
+#define grounded(ptr) (!is_flyer(ptr) && !is_floater(ptr) && !is_clinger(ptr))
 #define is_swimmer(ptr) (((ptr)->mflags1 & M1_SWIM) != 0L)
 #define breathless(ptr) (((ptr)->mflags1 & M1_BREATHLESS) != 0L)
 #define amphibious(ptr) \

include/patchlevel.h

@@ -17,7 +17,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 49
+#define EDITLEVEL 50
 
 /*
  * Development status possibilities.

src/hack.c

@@ -13,6 +13,7 @@ static void dosinkfall(void);
 static boolean findtravelpath(int);
 static boolean trapmove(int, int, struct trap *);
 static void check_buried_zombies(xchar, xchar);
+static boolean swim_move_danger(xchar x, xchar y);
 static void domove_core(void);
 static void maybe_smudge_engr(int, int, int, int);
 static struct monst *monstinroom(struct permonst *, int);
@@ -1519,6 +1520,46 @@ check_buried_zombies(xchar x, xchar y)
     }
 }
 
+/* Is it dangerous for hero to move to x,y due to water or lava? */
+static boolean
+swim_move_danger(xchar x, xchar y)
+{
+    if (!Levitation && !Flying && grounded(g.youmonst.data) && !Stunned
+        && !Confusion && levl[x][y].seenv
+        && ((is_pool(x, y) && !is_pool(u.ux, u.uy))
+            || (is_lava(x, y) && !is_lava(u.ux, u.uy)))) {
+        boolean known_wwalking, known_lwalking;
+
+        known_wwalking = (uarmf && uarmf->otyp == WATER_WALKING_BOOTS
+                          && objects[WATER_WALKING_BOOTS].oc_name_known
+                          && !u.usteed);
+        known_lwalking = (known_wwalking && Fire_resistance &&
+                          uarmf->oerodeproof && uarmf->rknown);
+        /* FIXME: This can be exploited to identify the ring of fire resistance
+        * if the player is wearing it unidentified and has identified
+        * fireproof boots of water walking and is walking over lava. However,
+        * this is such a marginal case that it may not be worth fixing. */
+        if ((is_pool(x, y) && !known_wwalking)
+            || (is_lava(x, y) && !known_lwalking)) {
+            if (g.context.nopick) {
+                /* moving with m-prefix */
+                g.context.swim_tip = TRUE;
+                return FALSE;
+            } else if (ParanoidSwim) {
+                You("avoid stepping into the %s.",
+                    waterbody_name(x, y));
+                if (!g.context.swim_tip) {
+                    pline("(Use '%s' prefix to step in if you really want to.)",
+                          visctrl(cmd_from_func(do_reqmenu)));
+                    g.context.swim_tip = TRUE;
+                }
+                return TRUE;
+            }
+        }
+    }
+    return FALSE;
+}
+
 void
 domove(void)
 {
@@ -1946,6 +1987,13 @@ domove_core(void)
         return;
     }
 
+    /* Is it dangerous to swim in water or lava? */
+    if (swim_move_danger(x, y)) {
+        g.context.move = 0;
+        nomul(0);
+        return;
+     }
+
     /* Move ball and chain.  */
     if (Punished)
         if (!drag_ball(x, y, &bc_control, &ballx, &bally, &chainx, &chainy,

src/options.c

@@ -154,6 +154,8 @@ static const struct paranoia_opts {
       "y to pray (supersedes old \"prayconfirm\" option)" },
     { PARANOID_REMOVE, "Remove", 1, "Takeoff", 1,
       "always pick from inventory for Remove and Takeoff" },
+    { PARANOID_SWIM, "swim", 1, 0, 0,
+      "avoid walking into lava or water" },
     /* for config file parsing; interactive menu skips these */
     { 0, "none", 4, 0, 0, 0 }, /* require full word match */
     { ~0, "all", 3, 0, 0, 0 }, /* ditto */